dockerTools.streamLayeredImage: fix enableFakechroot (#429601)

Changed files
+2
pkgs
build-support
docker
+2
pkgs/build-support/docker/default.nix
···
"/proc/"
"/sys/"
"${builtins.storeDir}/"
+
"$NIX_BUILD_TOP"
"$out/layer.tar"
);
···
--exclude=./proc \
--exclude=./sys \
--exclude=.${builtins.storeDir} \
+
--exclude=".$NIX_BUILD_TOP" \
--numeric-owner --mtime "@$SOURCE_DATE_EPOCH" \
--hard-dereference \
-cf $out/layer.tar .